The typical manufacturing method and groove configuration of hot-formed banded pistons are shown in Storms U.S. Pat. No. 3,212,411 granted Oct. 19, 1965. Its hot-forming and cooling tubes first hot-form the material to a piston periphery and then cool it in order to retain the formed cylindrical shape. The grooves are generally like the sixty degree screw threads commonly known as American National Standard. With but very few exceptions, this is also believed to have been the thread shape and angle norm in the banded piston industry since the advent of the Storms invention almost thirty years ago. One recent exception is a "square" grooved piston which has been reported to have originated in Japan.
Whether the grooves are of the type depicted in the aforementioned Storms patent, square-grooved or anything in between, it is unlikely that with the conventional hot-forming technology used to manufacture banded pistons, the grooves can be sufficiently filled with material to reduce or eliminate "blow-by". The latter term is used in the piston-banding industry to describe a popping-off of the band from the piston due to an extremely high hydraulic or pneumatic shock load applied from the side of the piston opposite its head end while performing in a fluid cylinder.